1. Without trading Sale we can rebuild in time for his contract to still be valuable (since every rebuilding year his cost is an unnecessary expense)

If the team is rebuilding, why would there be concern for an unnecessary expense for an ace? I'd only be concerned if I was looking to spend, and I wouldn't be looking to spend during a rebuild. He's only making an average of 4.75 mil in 2014 and 2015 (barely 3 million average if you include this year), and then eleven a year the next two. You'd pay more than that for a borderline #4 in the open market. Thornton was paid more for 2012-2013 than Sale will be paid for 2014-2015. It's not like the Sox are the Marlins and need to pair down payroll to 20 million in order to rebuild. Who are you saving that five mil for that is going to outproduce Sale?

If you want to argue that whoever he returns is going to be collectively be more productive in the long run that's one thing, but the unnecessary expense argument is pretty weak considering Sale's contract.

Now Danks' contract, on the other hand, I would dump for a bag of balls.